JP2018521582A - Method and apparatus for efficient data transmission in a half-duplex communication system with large propagation delay - Google Patents

Abstract

Methods and apparatus are provided for efficient transmission of data by a half-duplex transceiver in a satellite communication system. To reduce the amount of guard time required to separate the return link transmission from the forward link reception by the user terminal half-duplex transceiver, the time reference for the return link is skewed with respect to the time reference for the forward link. There is a time lag. The guard time is determined based on the maximum round-trip propagation delay difference and the half-duplex transceiver transition time for switching between transmit and receive modes. In satellite communication systems where there are a large number of active user terminals in beam coverage, a random time offset is applied to spread approximately equal traffic loads across the time offset.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This patent application is assigned to the “METHOD AND APPARATUS FOR EFFICIENT DATA” filed on July 2, 2015, which is assigned to the assignee of the present application and is expressly incorporated herein by reference in its entirety. Claims priority of US Provisional Application No. 62 / 188,317 entitled "TRANSMISIONS IN HALF-DUPLEX COMMUNICATION SYSTEMS WITH LARGE PROPAGATION DELAYS".

Introduction The various aspects described herein relate to communication systems, and more particularly, to data transmission in a half-duplex communication system with large propagation delay.

  Conventional satellite-based communication systems include a gateway and one or more satellites for relaying communication signals between the gateway and one or more user terminals. The gateway is a ground station having an antenna for transmitting a signal to a communication satellite and receiving a signal from the communication satellite. A gateway is a communication link that uses satellites to connect user terminals to other user terminals or users of other communication systems such as the public switched telephone network, the Internet, and various public and / or private networks. I will provide a. Satellites are orbiting receivers and repeaters that are used to relay information.

  As long as the user terminal is within the “footprint” of the satellite, the satellite can receive signals from the user terminal and transmit signals to the user terminal. The satellite footprint is a geographical area on the surface within the satellite signal. The footprint is usually geographically divided into “beams” by using beamforming antennas. Each beam covers a specific geographic area within the footprint. The beams can be directed so that two or more beams from the same satellite cover the same specific geographic area.

  Geostationary satellites have long been used for communications. A geostationary satellite is stationary relative to a given position on the earth, and therefore there is little timing shift and Doppler frequency shift in radio signal propagation between a communications transceiver on the earth and a geostationary satellite. However, geostationary satellites are limited to geosynchronous orbits (GSOs), which are circles with a radius of approximately 42,164 km from the center of the earth directly above the equator of the earth, so the number of satellites that can be placed in the GSO is limited. The As an alternative to geostationary satellites, communication systems that utilize satellite placement in non-geostationary orbits, such as low earth orbit (LEO), have been devised to provide communication coverage for the entire earth or at least a large portion of the earth.

  A satellite communication system generally experiences a large propagation delay between a satellite and a ground station including a user terminal (UT) and a gateway due to the distance between the satellite and the ground station. Some satellite communication systems employ frequency division duplex (FDD), which allows ground station transceivers to receive and transmit simultaneously on these different radio frequencies if the different radio frequencies are sufficiently separated Make this possible in theory. However, in some FDD satellite communication systems, the frequency band is precious, so the frequency spacing between the receive and transmit frequency bands for a given ground station FDD transceiver may be small. In some cases, the receive and transmit frequencies for a given ground station may be too close for the duplexer to handle simultaneous reception and transmission of radio signals without interfering with each other.

  In a typical FDD communication system where the reception frequency band and the transmission frequency band are close to each other, the half-duplex reception and transmission scheme is a guard time between reception and transmission to avoid interference between the reception signal and the transmission signal. It is used with. For a given ground station, a half-duplex transceiver may be implemented to both receive and transmit radio signals, but not simultaneously. For example, a UT in a satellite communications network receives a forward link (FL) signal from a satellite and a return link (RL) signal to the satellite in a specified time slot or subframe of a given half-duplex (HD) frame. , And there may be a specific amount of guard time between the FL subframe and the RL subframe.

  In conventional half-duplex systems, a large amount of guard time is generally provided to ensure sufficient time separation between reception and transmission. A large amount of guard time in each HD frame results in wasted overhead and inefficiency because no information carrier signal can be received or transmitted during the guard time. Therefore, it is desirable to reduce guard time overhead and increase efficiency in half-duplex communication systems.

  Aspects of the present disclosure are directed to an apparatus and method for efficient data transmission in a half-duplex communication system with large propagation delay.

  In one aspect, a method for determining a return link time reference time lag relative to a forward link time reference in a satellite communication system is provided. The method includes determining a minimum round-trip propagation delay of a signal between a ground station and a satellite, and determining a transition time for the ground station half-duplex transceiver to switch between transmit and receive modes. Determining a system parameter based on a transition time for the half-duplex transceiver to switch between transmit mode and receive mode; a return link time relative to a forward link time reference based on the minimum round trip propagation delay and the system parameter Determining a reference time lag.

  In another aspect, an apparatus is provided that is configured to determine a time lag of a return link time reference relative to a forward link time reference in a satellite communication system. The apparatus comprises at least one processor and at least one memory coupled to the at least one processor, the at least one processor and the at least one memory being a minimum round-trip propagation of signals between the ground station and the satellite Determining the delay, determining the transition time for the ground station half-duplex transceiver to switch between transmit and receive modes, and half-duplex transceiver to switch between transmit and receive modes Determining a system parameter based on a transition time for determining a return link time reference time lag relative to a forward link time reference based on a minimum round trip propagation delay and the system parameter.

  In another aspect, an apparatus is provided for determining a return link time reference time lag relative to a forward link time reference in a satellite communication system. This device determines the minimum round-trip propagation delay of the signal between the ground station and the satellite and the transition time for the half-duplex transceiver at the ground station to switch between transmit and receive modes Means for determining a system parameter based on a transition time for the half-duplex transceiver to switch between transmit mode and receive mode, and a forward link based on the minimum round trip propagation delay and system parameter Means for determining a time lag of the return link time reference relative to the time reference.

  In another aspect, a computer-readable medium is provided that includes at least one instruction for causing a computer or processor to perform a method for determining a time lag of a return link time reference relative to a forward link time reference in a satellite communication system. This at least one command includes a command for determining the minimum round-trip propagation delay of the signal between the ground station and the satellite, and a transition for the ground station half-duplex transceiver to switch between transmit and receive modes. Instructions for determining time, instructions for determining system parameters based on transition time for the half-duplex transceiver to switch between transmit and receive modes, and based on minimum round trip propagation delay and system parameters And a command for determining a return link time reference time lag relative to the forward link time reference.

  In another aspect, a method is provided for determining a guard time between reception and transmission in a half-duplex transceiver. The method includes determining a maximum round trip propagation delay of the signal between the half duplex transceiver and the satellite, determining a minimum round trip propagation delay of the signal between the half duplex transceiver and the satellite, and a maximum round trip. Determining a maximum round-trip propagation delay difference based on the propagation delay and the minimum round-trip propagation delay; determining a transition time for the half-duplex transceiver to switch between transmit mode and receive mode; and maximum round-trip propagation delay. Determining a guard time based on a transition time for the difference and half-duplex transceiver to switch between transmit mode and receive mode.

  In another aspect, an apparatus is provided that is configured to determine a guard time between reception and transmission at a half-duplex transceiver. The apparatus comprises at least one processor and at least one memory coupled to the at least one processor, wherein the at least one processor and at least one memory are configured to maximize a signal between the half-duplex transceiver and the satellite. Determine the round trip propagation delay, determine the minimum round trip propagation delay of the signal between the half duplex transceiver and the satellite, and determine the maximum round trip propagation delay difference based on the maximum round trip propagation delay and the minimum round trip propagation delay Determining the transition time for the half-duplex transceiver to switch between transmit and receive modes, and the maximum round-trip propagation delay difference and half-duplex transceiver to switch between transmit and receive modes And determining the guard time based on the transition time for.

  In another aspect, an apparatus is provided for determining a guard time between reception and transmission at a half-duplex transceiver. The apparatus includes means for determining a maximum round trip propagation delay of a signal between a half duplex transceiver and a satellite, and means for determining a minimum round trip propagation delay of a signal between the half duplex transceiver and the satellite. Means for determining the maximum round trip propagation delay difference based on the maximum round trip propagation delay and the minimum round trip propagation delay, and for determining the transition time for the half-duplex transceiver to switch between transmit mode and receive mode. And means for determining a guard time based on a maximum round-trip propagation delay difference and a transition time for the half-duplex transceiver to switch between transmit and receive modes.

  In another aspect, a computer-readable medium is provided that includes at least one instruction for causing a computer or processor to perform a method for determining a guard time between reception and transmission in a half-duplex transceiver. This at least one instruction determines the maximum round-trip propagation delay of the signal between the half-duplex transceiver and the satellite and the minimum round-trip propagation delay of the signal between the half-duplex transceiver and the satellite. Instructions for determining the maximum round-trip propagation delay difference based on the maximum and minimum round-trip propagation delays, and the transition time for the half-duplex transceiver to switch between transmit and receive modes. Instructions for determining, and instructions for determining a guard time based on a maximum round trip propagation delay difference and a transition time for the half duplex transceiver to switch between transmit and receive modes.

  In another aspect, a method for determining forward link duration and guard duration in a half-duplex frame is provided. The method includes allocating a forward link time segment in a special subframe of a half-duplex frame, allocating a guard time segment in the special subframe, and a half-duplex frame based on the forward link time segment in the special subframe. Determining a forward link duration in the medium, and determining a guard duration in the half-duplex frame based on a guard time segment in the special subframe.

  In another aspect, an apparatus is provided that is configured to determine a forward link duration and a guard duration in a half-duplex frame in a satellite communication system. The apparatus comprises at least one processor and at least one memory coupled to the at least one processor, wherein the at least one processor and the at least one memory are forward link time segments in a special subframe of a half-duplex frame. Assigning a guard time segment in a special subframe, determining a forward link duration in a half-duplex frame based on a forward link time segment in the special subframe, and in a special subframe Determining a guard duration in the half-duplex frame based on the guard time segment.

  In another aspect, an apparatus is provided for determining a forward link duration and a guard duration in a half-duplex frame in a satellite communication system. The apparatus is based on means for allocating forward link time segments in special subframes of half duplex frames, means for allocating guard time segments in special subframes, and forward link time segments in special subframes. Means for determining a forward link duration in a half-duplex frame and means for determining a guard duration in a half-duplex frame based on a guard time segment in a special subframe.

  In another aspect, a computer-readable medium comprising at least one instruction for causing a computer or processor to perform a method for determining forward link duration and guard duration in a half-duplex frame in a satellite communication system is provided. Is done. The at least one instruction includes an instruction to allocate a forward link time segment in a special subframe of a half-duplex frame, an instruction to allocate a guard time segment in a special subframe, and a forward link time segment in the special subframe. And instructions for determining a forward link duration in a half-duplex frame based on and a guard duration in a half-duplex frame based on a guard time segment in a special subframe. .

  In another aspect, a method is provided for scheduling time offsets of a plurality of user terminals during satellite beam coverage in a satellite communication system. The method includes determining a number of time offsets based on the number of active user terminals in beam coverage, assigning equally spaced time offsets based on the number of time offsets, and in beam coverage. Determining whether an aggregate pattern for the active user terminal has a random offset and spreading an approximately equal traffic load over time for the active user terminal.

  In another aspect, an apparatus is provided that is configured to schedule time offsets of a plurality of user terminals during satellite beam coverage in a satellite communication system. The apparatus comprises at least one processor and at least one memory coupled to the at least one processor, the at least one processor and the at least one memory based on the number of active user terminals in beam coverage. Determining the number of time offsets, assigning equally spaced time offsets based on the number of time offsets, and whether the aggregate pattern for active user terminals in beam coverage has a random offset And spreading substantially equal traffic loads over time for active user terminals.

  In another aspect, an apparatus is provided for scheduling time offsets of a plurality of user terminals during satellite beam coverage in a satellite communication system. The apparatus includes means for determining a number of time offsets based on the number of active user terminals in beam coverage, means for assigning equally spaced time offsets based on the number of time offsets, Means for determining whether an aggregate pattern for active user terminals in beam coverage has a random offset; and means for spreading substantially equal traffic load over time for active user terminals. Including.

  In another aspect, a computer readable medium is provided that includes at least one instruction for causing a computer or processor to perform a method of scheduling time offsets of a plurality of user terminals during satellite beam coverage in a satellite communication system. The at least one instruction is for determining a number of time offsets based on the number of active user terminals in beam coverage and for assigning equally spaced time offsets based on the number of time offsets. Instructions for determining whether an aggregate pattern for active user terminals in beam coverage has a random offset, and for spreading an approximately equal traffic load over time for active user terminals Including instructions.

  The accompanying drawings are presented to aid in the description of aspects of the present disclosure and are provided for illustration of the aspects only, and not limitation of the aspects.

It is a block diagram of an example of a communication system. FIG. 2 is a block diagram of an example of the gateway in FIG. FIG. 2 is a block diagram of an example of the satellite of FIG. FIG. 2 is a block diagram of an example of a user terminal in FIG. FIG. 2 is a block diagram of an example of user equipment in FIG. It is a figure which shows an example of a half duplex (HD) frame. FIG. 7 is a diagram illustrating an example of a special subframe (SSF) in the HD frame of FIG. FIG. 6 is a diagram illustrating an example of a hybrid automatic repeat request (HARQ) timeline with a feeder link delay of approximately 9.2 ms. It is a figure which shows an example of the HARQ timeline which has a feeder link delay of about 4 ms. FIG. 6 is a block diagram illustrating an example of a module for determining the amount of guard time in an HD frame. FIG. 6 is a block diagram illustrating an example of a module for skewing a return link time reference with respect to a forward link time reference. It is a block diagram which shows an example of the module for determining the half-duplex transmission / reception pattern in a user terminal. It is a block diagram which shows an example of a random offset scheduler. It is a block diagram which shows an example of an adaptive SSF scheduler. 6 is a flowchart illustrating a method for determining a return link time reference time lag relative to a forward link time reference in a satellite communication system. FIG. 5 is a flowchart illustrating a method for determining a guard time between reception and transmission in a half-duplex transceiver. 6 is a flowchart illustrating a method for determining a forward link duration and a guard duration in a half-duplex frame in a satellite communication system. 6 is a flowchart illustrating a method for scheduling time offsets of a plurality of user terminals during satellite beam coverage in a satellite communication system.

  Various aspects of the disclosure provide for a user terminal (UT) communicating with a gateway through a satellite in a non-geostationary satellite communication system, such as a low earth orbit (LEO) satellite communication system for data, voice, or video communication. ) For the synchronization of the time or frequency of the radio signal transmitted. In one aspect, the time of transmission of wireless signals from user terminals may be adjusted so that they arrive at the gateway at the same time or with arrival time differences that are within a specified tolerance. . In another aspect, the carrier frequency of the radio signal transmitted from the user terminal is such that the difference in frequency offset at the gateway is eliminated, including but not limited to the difference in Doppler offset, or at least within a specified tolerance. It can be adjusted to be reduced to a quantity. In one aspect, an open-loop pre-correction is performed to generate a time or frequency pre-correction value, which can adjust the transmission time to equalize the propagation delay or reduce the frequency offset difference. It can be applied to adjust the carrier frequency to remove or reduce. In another aspect, closed-loop pre-correction is performed in addition to open-loop pre-correction to provide a more accurate correction value for time or frequency. In yet another aspect, a satellite communication system may have a large number of active user terminals present in beam coverage. A random time offset can be applied by the scheduler to spread approximately equal traffic load across the time offset. Various other aspects of the disclosure are also described in further detail below.

  Aspects of the present disclosure are described in the following description and related drawings directed to specific embodiments. Alternate embodiments may be devised without departing from the scope of the present disclosure. In addition, well-known elements are not described in detail or are omitted so as not to obscure the relevant details of the disclosure.

  The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects. Similarly, the term “aspect” does not require that all aspects include the discussed features, advantages, or modes of operation.

  The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms `` comprises, comprising '' or `` includes, including '' as used herein, describe the presence of the stated feature, integer, step, action, element, or component. It will be further understood that, although explicitly indicated, it does not exclude the presence or addition of one or more other features, integers, steps, actions, elements, components, or groups thereof. In addition, the term “or” has the same meaning as the Boolean operator “OR”, ie, includes the possibility of “any” and “both”, and unless otherwise specified, “exclusive logic” It should be understood that it is not limited to “sum” (“XOR”). It is also to be understood that the symbol “/” between two adjacent words has the same meaning as “or” unless stated otherwise. Furthermore, phrases such as “connected to”, “coupled to”, or “communicating with” are not limited to direct connections, unless explicitly stated otherwise.

  Moreover, many aspects are described in terms of a series of actions to be performed by, for example, elements of a computing device. The various actions described herein are specific circuits such as a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DPS), an application specific integrated circuit (ASIC), a field programmable gate array. (FPGA), or may be executed by various other types of general purpose or special purpose processors or circuits, executed by program instructions executed by one or more processors, or executed by a combination of both It will be appreciated that In addition, these series of actions described herein may be performed in any form of computer-readable storage that stores a corresponding set of computer instructions that, when executed, cause the associated processor to perform the functions described herein. It can be considered to be completely embodied in a storage medium. Accordingly, the various aspects of the disclosure may be embodied in a number of different forms, all considered to be within the scope of the claimed subject matter. Further, for each aspect described herein, the corresponding form of any such aspect may be described herein as, for example, "logic configured to" perform the operations described. is there.

  FIG. 1 illustrates a satellite communication system 100, including a plurality of satellites in non-geostationary orbit, e.g., low earth orbit (LEO) (although only one satellite 300 is shown for clarity of illustration) An example of a gateway 200 that communicates, a plurality of user terminals (UT) 400 and 401 that communicate with a satellite 300, and a plurality of user equipments (UE) 500 and 501 that respectively communicate with the UTs 400 and 401 is shown. In one aspect, the gateway 200 includes a scheduler 202, which may be, for example, an adaptive special subframe (SSF) scheduler and / or a random offset scheduler. Details regarding the scheduler 202 and related functions are provided in the following paragraphs and figures. In the example shown in FIG. 1, UT 400 and UE 500 communicate with each other via a bidirectional access link (having a forward access link and a return access link), and similarly, UT 401 and UE 501 have another bidirectional access link. Communicate with each other via In another implementation, one or more additional UEs (not shown) may only be configured to receive and thus communicate with the UT simply by using the forward access link. In another implementation, one or more additional UEs (not shown) may communicate with UT 400 and / or UT 401. Alternatively, the UT and the corresponding UE may be an integral part of a single physical device, such as a mobile phone with a built-in satellite transceiver and antenna for communicating directly with the satellite. Each UE 500 or 501 may be a user device such as a mobile device, phone, smartphone, tablet, laptop computer, computer, wearable device, smart watch, audiovisual device, or any device that includes the ability to communicate with UT. it can. Further, UE 500 and / or UE 501 can be a device (eg, access point, small cell, etc.) used to communicate with one or more end user devices.

  The gateway 200 may have access to the Internet 108 or one or more other types of public networks, semi-private networks, or private networks. In the example shown in FIG. 1, the gateway 200 is in communication with an infrastructure 106 that accesses the Internet 108 or one or more other types of public, semi-private, or private networks. can do. The gateway 200 may also be coupled to various types of communication backhaul including, for example, a landline network such as a fiber optic network or a public switched telephone network (PSTN) 110. Further, in alternative implementations, the gateway 200 interfaces with the Internet 108, the PSTN 110, or one or more other types of public, semi-private, or private networks without using the infrastructure 106. Sometimes. Still further, gateway 200 may communicate with other gateways, such as gateway 201, through infrastructure 106, or alternatively may be configured to communicate with gateway 201 without using infrastructure 106. is there. Infrastructure 106 may be wholly or partly network control center (NCC), satellite control center (SCC), wired and / or wireless core network, and / or satellite communication system 100 operation and / or satellite communication system 100. Any other component or system used to assist in communication with can be included.

  Communication between the satellite 300 and the gateway 200 in both directions is referred to as a feeder link, whereas communication between the satellite and each of the UTs 400 and 401 in both directions is referred to as a service link. The signal path from satellite 300 to a ground station, which can be gateway 200 or one of UTs 400 and 401, may be referred to generically as the downlink. The signal path from the ground station to the satellite 300 may be collectively referred to as the uplink. In addition, as shown, the signal can have general directionality, such as forward link and return link or reverse link. Thus, a communication link in the direction starting from gateway 200 and ending with UT400 through satellite 300 is called a forward link, whereas a communication link starting in UT400 and ending with gateway 200 through satellite 300 is called a return link or reverse link Called. Therefore, in FIG. 1, the signal path from the gateway 200 to the satellite 300 is labeled “forward link (FL)”, but the signal path from the satellite 300 to the gateway 200 is labeled “return link (RL)”. Is done. Similarly, in FIG. 1, the signal path from each UT 400 or 401 to the satellite 300 is labeled “Return Link (RL)”, but the signal path from the satellite 300 to each UT 400 or 401 is “forward link ( FL) ".

  FIG. 2 is an exemplary block diagram of gateway 200, which may also apply to gateway 201 of FIG. The gateway 200 includes several antennas 205, an RF subsystem 210, a digital subsystem 220, a public switched telephone network (PSTN) interface 230, a local area network (LAN) interface 240, a gateway interface 245, and a gateway controller 250. Is shown as RF subsystem 210 is coupled to antenna 205 and digital subsystem 220. Digital subsystem 220 is coupled to PSTN interface 230, LAN interface 240, and gateway interface 245. Gateway controller 250 is coupled to RF subsystem 210, digital subsystem 220, PSTN interface 230, LAN interface 240, and gateway interface 245.

  An RF subsystem 210, which can include several RF transceivers 212, an RF controller 214, and an antenna controller 216, can transmit communication signals to the satellite 300 via a forward link (FL) 301F and return A communication signal can be received from the satellite 300 via the link (RL) 301R. Although not shown for simplicity, each of the RF transceivers 212 can include a transmit chain and a receive chain. Each receive chain may include a low noise amplifier (LNA) and a downconverter (eg, a mixer) to amplify and downconvert received communication signals, respectively, in a known manner. In addition, each receive chain can include an analog-to-digital converter (ADC) for converting received communication signals from analog signals to digital signals (eg, for processing by the digital subsystem 220). . Each transmission chain may include an upconverter (eg, a mixer) and a power amplifier (PA) for upconverting and amplifying communication signals to be transmitted to the satellite 300, respectively, in a well-known manner. In addition, each transmit chain can include a digital-to-analog converter (DAC) for converting the digital signal received from the digital subsystem 220 into an analog signal to be transmitted to the satellite 300.

  The RF controller 214 may be used to control various aspects of the RF transceiver 212 (eg, carrier frequency selection, frequency and phase calibration, gain settings, etc.). The antenna controller 216 can control various aspects of the antenna 205 (eg, beamforming, beam steering, gain setting, frequency adjustment, etc.).

  The digital subsystem 220 may include a plurality of digital receiver modules 222, a plurality of digital transmitter modules 224, a baseband (BB) processor 226, and a control (CTRL) processor 228. The digital subsystem 220 can process communication signals received from the RF subsystem 210 and forward the processed communication signals to the PSTN interface 230 and / or the LAN interface 240, the PSTN interface 230 and / or the LAN interface The communication signal received from 240 can be processed and the processed communication signal can be forwarded to the RF subsystem 210.

  Each digital receiver module 222 may correspond to a signal processing element used to manage communication between the gateway 200 and the UT 400. One of the receive chains of the RF transceiver 212 can provide input signals to multiple digital receiver modules 222. Several digital receiver modules 222 may be used to handle all of the satellite beams and possible diversity mode signals that are processed at a given time. Although not shown for simplicity, each digital receiver module 222 may include one or more digital data receivers, searcher receivers, and diversity combiner and decoder modules. The searcher receiver may be used to search for the appropriate diversity mode of the carrier signal, and may be used to search for a pilot signal (or other relatively unchanged pattern strong signal) .

  Digital transmitter module 224 can process signals to be transmitted to UT 400 via satellite 300. Although not shown for simplicity, each digital transmitter module 224 may include a transmission modulator that modulates data for transmission. The transmit power of each transmit modulator is as follows: (1) applying a minimum level of power for interference reduction and resource allocation, and (2) compensating for attenuation and other path transmission characteristics in the transmit path Can be controlled by a corresponding digital transmit power controller (not shown for simplicity) that can apply an appropriate level of power.

  Control (CTRL) processor 228 coupled to digital receiver module 222, digital transmitter module 224, and BB processor 226 includes, but is not limited to, signal processing, timing signal generation, power control, handoff control, diversity combining, and Command and control signals can be provided to provide functions such as interfacing with the system.

  The CTRL processor 228 can also control pilot generation and power, synchronization, and paging channel signals and their coupling to the transmit power controller (not shown for simplicity). A pilot channel is a signal that is not modulated by data and can use a recurring, unchanging pattern or an unchanging frame structure type (pattern) or tone type input. For example, the orthogonal functions used to form the pilot signal channel generally have a known repetitive pattern, such as a constant value such as all ones or all zeros, or a scattered one and zero structured pattern.

  Baseband (BB) processor 226 is well known in the art and will not be described in detail herein. For example, the BB processor 226 may include various known elements such as (but not limited to) a coder, a data modem, and digital data switching and storage components.

  The PSTN interface 230 can provide communication signals to and receive communication signals from the external PSTN, either directly or through the additional infrastructure 106, as shown in FIG. The PSTN interface 230 is well known in the art and will not be described in detail herein. In other implementations, the PSTN interface 230 may be omitted or replaced by any other suitable interface that connects the gateway 200 to a terrestrial network (eg, the Internet 108).

  The LAN interface 240 can supply communication signals to the external LAN and receive communication signals from the external LAN. For example, the LAN interface 240 may be coupled to the Internet 108 directly or through additional infrastructure 106, as shown in FIG. The LAN interface 240 is well known in the art and will not be described in detail herein.

  The gateway interface 245 communicates communication signals to one or more other gateways associated with the satellite communication system 100 of FIG. 1 (and / or gateways associated with other satellite communication systems not shown for simplicity). From which a communication signal can be received. In some implementations, the gateway interface 245 can communicate with other gateways via one or more dedicated communication lines or channels (not shown for simplicity). In other implementations, the gateway interface 245 can communicate with other gateways using other networks (see also FIG. 1) such as the PSTN 110 and / or the Internet 108. In at least one implementation, the gateway interface 245 can communicate with other gateways via the infrastructure 106.

  Overall gateway control may be provided by the gateway controller 250. The gateway controller 250 can plan and control the use of resources of the satellite 300 by the gateway 200. For example, the gateway controller 250 can analyze trends, generate traffic plans, allocate satellite resources, monitor (or track) satellite positions, and monitor gateway 200 and / or satellite 300 performance. The gateway controller 250 also maintains and monitors the orbit of the satellite 300, relays satellite usage information to the gateway 200, tracks the position of the satellite 300, and / or adjusts the settings of various channels of the satellite 300, It can be coupled to a terrestrial satellite controller (not shown for simplicity).

  In the exemplary implementation shown in FIG. 2, gateway controller 250 includes a scheduler 202, which may be an adaptive special subframe (SSF) scheduler and / or a random offset scheduler. Details regarding the scheduler and related functions are provided in subsequent paragraphs and figures (see, eg, FIGS. 13 and 14). Scheduler 202 may provide information to RF subsystem 210, digital subsystem 220, and / or interfaces 230, 240, and 245. In one aspect, the information may be used in a satellite communication system having a large number of active user terminals for beam coverage. The random time offset is applied, for example, to spread an approximately equal traffic load across the time offset to facilitate communication between the gateway 200 and the UT 400 and UT 401.

  Similarly, in the exemplary implementation shown in FIG. 2, gateway controller 250 may optionally include a local time, frequency, and location reference 251 that includes RF subsystem 210, digital sub- System 220 and / or interfaces 230, 240, and 245 may be provided with local time or frequency information. The time or frequency information may be used to synchronize the various components of gateway 200 with each other and / or with satellite 300. Local time, frequency, and position criteria 251 may also provide satellite 300 position information (eg, ephemeris data) to various components of gateway 200. Further, although illustrated in FIG. 2 as being included in the gateway controller 250, in other implementations, the local time, frequency, and location reference 251 is provided to the gateway controller 250 (and / or the digital subsystem 220). And a separate subsystem coupled to one or more of the RF subsystems 210).

  Although not shown in FIG. 2 for simplicity, the gateway controller 250 may also be coupled to a network control center (NCC) and / or a satellite control center (SCC). For example, the gateway controller 250 may allow the SCC to communicate directly with the satellite 300, eg, retrieve ephemeris data from the satellite 300. Gateway controller 250 also directs gateway controller 250 to properly point antenna 205 (e.g., of satellite 300), schedule beam transmission, coordinate handover, and various other well-known functions. Processed information (eg, from SCC and / or NCC) can be received.

  FIG. 3 is an exemplary block diagram of satellite 300 for illustrative purposes only. It will be appreciated that specific satellite configurations can vary greatly and may or may not include on-board processing. Further, although shown as a single satellite, two or more satellites using inter-satellite communication can provide a functional connection between the gateway 200 and the UT 400. The present disclosure is not limited to any particular satellite configuration, and any satellite or combination of satellites that can provide a functional connection between the gateway 200 and the UT 400 may be considered within the scope of the present disclosure. It will be understood. In one example, satellite 300 includes forward transponder 310, return transponder 320, oscillator 330, controller 340, forward link antennas 352 (1) -352 (N), and return link antennas 361 (1) -361 (N). Is shown as A forward transponder 310 capable of processing communication signals in the corresponding channel or frequency band includes one of the first bandpass filters 311 (1) to 311 (N) and the first LNA 312 (1) to 312. Each of (N), one of frequency converters 313 (1) to 313 (N), one of each of second LNAs 314 (1) to 314 (N), and second bandpass filter 315 ( 1) to 315 (N) each and one each of PA316 (1) to 316 (N). Each of PAs 316 (1) -316 (N) is coupled to a respective one of antennas 352 (1) -352 (N).

  Within each of the respective forward paths FP (1) to FP (N), the first bandpass filter 311 (1) is a channel or frequency band of each forward path FP (1) to FP (N). The signal component having a frequency inside is passed, and the signal component having a frequency outside the channel or frequency band of each forward path FP (1) to FP (N) is filtered. Therefore, the passband of the first bandpass filter 311 (1) corresponds to the width of the channel associated with each forward path FP (1) to FP (N). The first LNA 312 (1) amplifies the received communication signal to a level appropriate for processing by the frequency converter 313 (1). The frequency converter 313 (1) converts the frequency of the communication signal in each of the forward paths FP (1) to FP (N) (for example, to a frequency suitable for transmission from the satellite 300 to the UT 400). The second LNA 314 (1) amplifies the frequency-converted communication signal, and the second bandpass filter 315 (1) filters signal components having frequencies other than the associated channel width. The PA 316 (1) amplifies the filtered signal to a power level suitable for transmission to the UT 400 via each antenna 352 (1) -352 (N). The return transponder 320 including a certain number N of return paths RP (1) to RP (N) receives communication signals from the UT 400 along the return link (RL) 302R via the antennas 361 (1) to 361 (N). Then, a communication signal is transmitted to the gateway 200 along the RL 301R via one or a plurality of antennas 362. Each of the return paths RP (1) to RP (N) capable of processing communication signals in the corresponding channel or frequency band is coupled to one of the antennas 361 (1) to 361 (N), respectively. Each one of the first bandpass filters 321 (1) to 321 (N), one each of the first LNA 322 (1) to 322 (N), the frequency converter 323 (1) to 323 ( N), each of the second LNAs 324 (1) -324 (N), and each of the second bandpass filters 325 (1) -325 (N).

  Among each of the return paths RP (1) to RP (N), the first bandpass filter 321 (1) is within the channel or frequency band of the respective return paths RP (1) to RP (N). Signal components having frequencies outside the channels or frequency bands of the respective return paths RP (1) to RP (N). Thus, in some implementations, the passband of the first bandpass filter 321 (1) corresponds to the width of the channel associated with each return path RP (1) -RP (N). The first LNA 322 (1) amplifies all received communication signals to a level appropriate for processing by the frequency converter 323 (1). The frequency converter 323 (1) converts the frequency of the communication signal in each of the return paths RP (1) to RP (N) (for example, to a frequency suitable for transmission from the satellite 300 to the gateway 200). The second LNA 324 (1) amplifies the frequency-converted communication signal, and the second bandpass filter 325 (1) filters signal components having frequencies other than the associated channel width. The signals from the return paths RP (1) to RP (N) are combined and supplied to one or more antennas 362 via the PA 326. The PA 326 amplifies the combined signal for transmission to the gateway 200.

  Oscillator 330, which may be any suitable circuit or device that generates an oscillation signal, provides forward local oscillator signal LO (F) to frequency converters 313 (1) -313 (N) of forward transponder 310; Return local oscillator signal LO (R) is provided to frequency converters 323 (1) -323 (N) of return transponder 320. For example, the LO (F) signal is used to convert the communication signal from the frequency band associated with the transmission of the signal from the gateway 200 to the satellite 300 to the frequency band associated with the transmission of the signal from the satellite 300 to the UT400. Can be used by transducers 313 (1) -313 (N). LO (R) signal is a frequency converter to convert communication signals from the frequency band associated with the transmission of signals from UT 400 to satellite 300 to the frequency band associated with the transmission of signals from satellite 300 to gateway 200 323 (1) -323 (N) may be used.

  A controller 340 coupled to the forward transponder 310, the return transponder 320, and the oscillator 330 can control various operations of the satellite 300, including (but not limited to) channel allocation. In one aspect, the controller 340 can include a memory (not shown for simplicity) coupled to the processor. The memory, when executed by the processor, stores instructions that cause the satellite 300 to perform operations, including but not limited to operations described herein (e.g., EPROM, One or more non-volatile memory elements, such as EEPROM, flash memory, hard drive, etc.

  An example of a transceiver for use with a UT400 or 401 is shown in FIG. In FIG. 4, at least one antenna 410 is provided for receiving a forward link communication signal (e.g., from satellite 300), where the forward link communication signal is transmitted to an analog receiver 414 where it is downconverted and amplified, Digitized. A duplexer element 412 is often used to allow the same antenna 410 to provide both transmit and receive functions. Alternatively, the transceiver for UT 400 or 401 can utilize separate antennas 410 to operate at different transmit and receive frequencies.

  Digital communication signals output by the analog receiver 414 are transmitted to at least one digital data receiver 416A-416N and at least one searcher receiver 418. As will be apparent to those skilled in the art, the digital data receivers 416A-416N can be used to obtain a desired level of signal diversity, depending on an acceptable level of transceiver complexity.

  At least one user terminal control processor 420 is coupled to the digital data receivers 416A-416N and the searcher receiver 418. The control processor 420 provides, among other functions, basic signal processing, timing, power and handoff control or coordination, and selection of frequencies used for signal carriers. Another basic control function that can be performed by the control processor 420 is the selection or manipulation of functions to be used to process various signal waveforms. Signal processing by the control processor 420 can include determining relative signal strength and calculating various associated signal parameters. Such calculation of signal parameters such as timing and frequency can include the use of additional or separate dedicated circuitry to provide increased efficiency or speed in measurement or improved allocation of control processing resources.

  The outputs of digital data receivers 416A-416N are coupled to a digital baseband circuit 422 in UT400. Digital baseband circuit 422 includes, for example, processing and presentation elements used to transmit information to and from UE 500 as shown in FIG. Referring to FIG. 4, when diversity signal processing is used, the digital baseband circuit 422 may include a diversity combiner and decoder. Some of these elements may also operate under control of the control processor 420 or in communication with the control processor 420.

  When voice data or other data is prepared as an output message or communication signal starting from UT400, the digital baseband circuit 422 receives, stores, processes and otherwise prepares the desired data for transmission. Used for. Digital baseband circuit 422 provides this data to transmit modulator 426 operating under the control of control processor 420. The output of transmit modulator 426 is transmitted to digital transmit power controller 428, which provides output power control to analog transmit power amplifier 430 for final transmission of the output signal from antenna 410 to the satellite (eg, satellite 300). Is done.

  In FIG. 4, the UT transceiver also includes a memory 432 associated with the control processor 420. Memory 432 may include instructions for execution by control processor 420 as well as data for processing by control processor 420. In the example shown in FIG. 4, the memory 432 may include instructions for performing time or frequency adjustments to be applied to the RF signal to be transmitted by the UT 400 via the RL 301R to the satellite 300.

  In the example shown in FIG. 4, the UT 400 also includes an optional local time, frequency, and / or location reference 434 (e.g., a GPS receiver), which is local time, frequency, and / or location. This information can be provided to the control processor 420 for a variety of applications including, for example, time or frequency synchronization for the UT 400.

  Digital data receivers 416A-416N and searcher receiver 418 are comprised of signal correlation elements for demodulating and tracking specific signals. The searcher receiver 418 is used to search for pilot signals or other relatively unchanged pattern strong signals, while the digital data receivers 416A-416N are other signals associated with detected pilot signals. Used to demodulate. However, the digital data receivers 416A-416N can be assigned to track the pilot signal after acquisition to accurately determine the ratio of signal chip energy to signal noise and formulate pilot signal strength. Thus, the outputs of these digital data receivers 416A-416N can be monitored to determine the energy or frequency of the pilot signal or other signal. These digital data receivers 416A-416N also employ frequency tracking elements that can be monitored to provide current frequency and timing information to the control processor 420 for signal demodulation.

  The control processor 420 can use such information to determine to what extent the received signal is offset from the oscillator frequency when scaled to the same frequency band, as appropriate. This information and other information regarding frequency error and frequency shift can be stored in storage or memory 432 as required.

  Control processor 420 may also be coupled to UE interface circuit 450 to allow communication between UT 400 and one or more other UEs (not shown). The UE interface circuit 450 may be configured as desired for communication with various UE configurations, and thus varies depending on the various communication techniques utilized to communicate with various supported UEs. A transceiver and associated components can be included. For example, the UE interface circuit 450 may include one or more antennas, a wide area network (WAN) transceiver, a wireless local area network (WLAN) transceiver, a local area network (LAN) interface, a public switched telephone network (PSTN) interface (not shown). And / or other known communication techniques configured to communicate with one or more UEs communicating with the UT 400.

  FIG. 5 is a block diagram illustrating an example of UE 500, which may also apply to UE 501 of FIG. The UE 500 shown in FIG. 5 may be, for example, a mobile device, a handheld computer, a tablet, a wearable device, a smartwatch, or any type of device that can interact with a user. In addition, UE 500 may be a network-side device that provides connectivity to various final end-user devices and / or various public or private networks. In the example shown in FIG. 5, UE 500 includes a LAN interface 502, one or more antennas 504, a wide area network (WAN) transceiver 506, a wireless local area network (WLAN) transceiver 508, and a satellite positioning system (SPS) receiver 510. Can be included. The SPS receiver 510 may be compatible with a global positioning system (GPS), a global navigation satellite system (GLONASS), and / or any other global or regional satellite-based positioning system. In an alternative aspect, the UE 500 may include a WLAN transceiver 508, such as a Wi-Fi transceiver with or without a LAN interface 502, a WAN transceiver 506, and / or an SPS receiver 510, for example. Further, UE 500 may include additional transceivers such as Bluetooth®, ZigBee® and other known technologies, WAN transceiver 506, WLAN transceiver 508, and / or SPS with or without LAN interface 502. A receiver 510 can be included. Accordingly, the elements shown for UE 500 are provided as exemplary configurations only and are not intended to limit the configuration of UEs in accordance with various aspects disclosed herein.

  In the example shown in FIG. 5, processor 512 is connected to LAN interface 502, WAN transceiver 506, WLAN transceiver 508, and SPS receiver 510. In some cases, motion sensor 514 and other sensors may also be coupled to processor 512.

  The memory 516 is connected to the processor 512. In one aspect, the memory 516 can include data 518 that can be transmitted to and / or received from the UT 400, as shown in FIG. Referring to FIG. 5, the memory 516 can also include stored instructions 520 that are to be executed by the processor 512 to perform, for example, processing steps for communicating with the UT 400. In addition, UE 500 can also include a user interface 522, which includes hardware for interfacing the input or output of processor 512 to the user, for example, via light, sound, or haptic input or output, and Software can be included. In the example shown in FIG. 5, UE 500 includes a microphone / speaker 524 connected to a user interface 522, a keypad 526, and a display 528. Alternatively, the user's haptic input or output may be integrated into the display 528, for example by using a touch screen display. Again, the elements shown in FIG. 5 are not intended to limit the UE configurations disclosed herein, and the elements included in UE 500 are based on the final usage of the device and the design choices of the system engineer. It will be understood that it will change.

  Further, UE 500 may be a user device such as, for example, a mobile device or an external network side device that communicates with UT 400 as shown in FIG. Alternatively, UE 500 and UT 400 may be an integral part of a single physical device.

  In the example shown in FIG. 1, the two UTs 400 and 401 can perform bidirectional communication with the satellite 300 via RL and FL in beam coverage. The satellite 300 can communicate with more than two UTs 400 and 401 in beam coverage. Therefore, the RL from UT 400 and 401 to satellite 300 is a many-to-one channel. Large time delay differences and frequency offset differences may exist between different UTs in the beam coverage. The difference in frequency offset may be due to, for example, the difference in Doppler frequency shift experienced by UTs 400 and 401 in beam coverage due to the relative movement of satellite 300 and UTs 400 and 401. For example, some UTs 400 and 401 may be mobile and other UTs may be fixed. Differences in frequency offset between different UT400s and 401s can also be caused by other factors, for example, frequency drift due to radio frequency (RF) components in some transmitter chains of UT400s and 401s during beam coverage. is there.

  In the satellite communication system 100 shown in FIG. 1, multiple UTs 400 and 401 in beam coverage may be multiplexed by time division multiplexing (TDM), frequency division multiplexing (FDM), or some other method. . Regardless of whether the multiplexing of different UTs 400 and 401 in beam coverage is achieved by TDM, FDM, or some other type of multiplexing, the amount of unidirectional propagation delay, i.e., the radio signal between the UT and the satellite The amount of time that travels in one direction between can be in the range of about 4 ms to about 5.2665 ms, depending on the distance between the satellite and the UT.

  In this example, the round trip delay for a single propagation in the satellite communication system 100 can be on the order of 10.533 ms. If the guard time between the reception period and transmission period of a given UT is equal to the maximum round trip delay, the reception period and transmission period must be much longer to reduce the guard time overhead.

  In one aspect, a method and apparatus for skewing a timing reference is provided to reduce the guard time required to separate the receive and transmit operations of a UT half-duplex transceiver. In one aspect, if the RL time reference is skewed with respect to the FL time reference by a minimum round trip delay (RTD) of 8 ms, for example, there is a time lag, the guard time required for the half-duplex transceiver is the maximum RTD Difference 2.533 ms, plus, the time required for a half-duplex transceiver to transition from receive mode to transmit mode and from transmit mode to receive mode. In contrast to other schemes for efficient half-duplex FDD operation, methods and apparatus according to various aspects of the present disclosure may be used for any portion of a symbol, e.g., for orthogonal frequency division multiplexing (OFDM) symbols. There is no need to discard the cyclic prefix.

  FIG. 6 is a diagram illustrating an example of a reception / transmission pattern of a half-duplex (HD) frame for a half-duplex UT transceiver. In this example, the HD frame has a duration of 10ms, FL "F", followed by Special Subframe (SSF) "S", followed by guard time "G", followed by RL "R" Including four time segments or subframes.

  In one aspect, such HD frame formats, including F, S, G, and R subframes, are FL subframes and RL subframes due to constraints in FL and RL hybrid automatic repeat request (HARQ) acknowledgments and RL scheduling grants. Allows one-to-one association with frames. In this example, where the HD frame has a duration of 10 ms, the time allocation for subframes F, S, G, and R is 3 ms, 1 ms, 2 ms, and 4 ms, respectively.

FIG. 7 is a diagram illustrating an example of a special subframe (SSF), that is, a subframe S in the HD frame of FIG. In one aspect, the SSF includes the first part, ie, the FL component F _SSF immediately after the FL subframe F shown in FIG. 6, and the second part, ie, the guard immediately before the guard subframe G shown in FIG. Includes time component G _SSF . In the SSF of the example shown in FIG. 7, the FL component F _SSF is a time segment designated as FL, and the guard time component G _SSF is a time segment designated as a guard time.

For example, if the duration of an HD frame is 10 ms, the SSF includes an F _SSF that has a duration of about 0.2 ms for the FL and a G _SSF that has a duration of about 0.8 ms for the guard time. May have a duration. In this example, the total guard time is the sum of the guard time component G _SSF in the SSF shown in FIG. 7 and the guard time in the subframe G shown in FIG. 6, and is about 2.8 ms. Similarly, the total duration of FL is the sum of the duration of FL component F _SSF and subframe F in the _SSF, and is about 3.2 ms in this example. In one embodiment, the ratio of the FL component F _SSF for guard time component G _SSF in SSF, as described in more detail below, may be dynamically adjusted.

  As is apparent from FIG. 6, the guard time subframe G needs to have a much shorter duration than the HD frame. In one aspect, the minimum guard time required in an HD frame for a half-duplex transceiver must account for additional delay due to transition from receive mode to transmit mode by the half-duplex transceiver and vice versa. The maximum round-trip propagation delay difference, that is, the maximum round-trip propagation delay minus the minimum round-trip propagation delay. The maximum round-trip propagation delay is about 10.533 ms and the minimum round-trip propagation delay is about 8 ms. In the example described above, the maximum round-trip propagation delay difference is 10.533 ms−8 ms = 2.533 ms. In one aspect, the transition from receive mode to transmit mode by the half-duplex transceiver and vice versa in deriving the guard time required to separate transmission of the return link signal and reception of the forward link signal Is added to the maximum round-trip propagation delay difference.

  In a typical half-duplex transceiver, when the transceiver switches from transmit mode to receive mode or vice versa, circuit components such as phase-locked loops (PLLs) and power amplifiers (PAs) stabilize for a finite time. It can cost an amount. In one aspect, an additional time margin may be provided in the guard time to accommodate the time required for transition from transmit mode to receive mode and vice versa. For example, a typical half-duplex transceiver may require about 100 μs transition time from transmit mode to receive mode for the PLL and PA to be stable. In such a typical half-duplex transceiver, the transition time from the reception mode to the transmission mode for the PLL and PA to stabilize is also about 100 μs.

  In one aspect, the guard time required for a half-duplex transceiver in the UT is equal to the maximum round-trip propagation delay difference, the plus receive mode to transmit mode transition time, and the plus transmit mode to receive mode transition time. In the example described above where the maximum round-trip propagation delay difference is about 2.533 ms and the transition time for each half-duplex transition between transmit and receive modes in either direction is about 100 μs, The guard time for the dual transceiver is at least 2.533 ms + 0.1 ms + 0.1 ms = 2.733 ms and can be rounded up to 2.8 ms.

  In one aspect, in order to reduce the amount of time required for subframe G in each HD frame, the time reference for RL is skewed by a set amount with respect to the time reference for FL. In other words, there may be a time lag. In one aspect, as will be described in more detail below, the minimum round-trip propagation delay, ie, an amount approximately equal to twice the minimum propagation delay of one-way signal movement between the UT and the satellite, minus, transmission mode and reception. Only a small adjustment value to account for the transition time required by the half-duplex transceiver to switch between modes, the time reference for RL is skewed or time lag with respect to the time reference for FL There may be.

  In one aspect, the time reference for RL may be skewed or have a time lag by an amount slightly less than the minimum round trip propagation time relative to the time reference for FL. For example, if the minimum one-way propagation delay is about 4 ms, the time reference for RL may be skewed by about 8 ms, minus, a small adjustment value with respect to the time reference for FL, A system parameter based on transition time for the dual transceiver to switch between transmit mode and receive mode.

The amount of time-based time lag or skew for RL to FL may be set equal to the minimum round-trip propagation delay minus T _R2F , which is _required for the half-duplex transceiver to switch from transmit mode to receive mode It is a system parameter based on the transition time. For example, when a half-duplex transceiver switches from transmit mode to receive mode or vice versa, if the transition time for the transceiver components such as PLL and PA to stabilize is about 100 μs, the system parameter T _R2F It may be slightly more than 100 μs to accommodate the time margin.

In the example described above for an HD frame having a length of 10 ms and including F, S, G, and R subframes, subframe S includes FL time component F _SSF and guard time component G _SSF. It is a special subframe (SSF), and the lengths of the F, S, G, and R subframes are 3 ms, 1 ms, 2 ms, and 4 ms, respectively, as shown in FIGS. If the FL time component F _SSF has a length of 0.2 ms and the guard time component G _SSF has a length of 0.8 ms, the total duration allocated to the FL in the HD frame is 3 ms + 0.2 ms = 3.2 ms Thus, the total duration allocated to the guard time is 2.8 ms, and the total duration allocated to the RL remains 4 ms, which is the length of the R subframe. In this example, the UT can achieve 32% of FL beam capacity and 40% of RL beam capacity.

  In one aspect, multiple random offsets may be utilized in the half-duplex pattern of the HD frame for multiple UTs in beam coverage. In the example described above, where the HD frame has a length of 10 ms, 10 equal time offsets, for example 0 ms, 1 ms, 2 ms,... It may be provided in a half-duplex pattern. In one aspect, the UT half-duplex transceiver may monitor the FL when there is no traffic. When FL and / or RL traffic for a UT arrives, the half-duplex pattern for that UT begins with a random offset that can be any of an offset from 0 ms to 9 ms. When the traffic burst ends, the UT enters a state for FL monitoring. The next time FL and / or RL traffic for the UT arrives, the half-duplex pattern for the UT begins with another random offset that may differ from the previous offset. For any UT in beam coverage, the HD frame offset varies randomly with time following the random arrival time of FL and / or RL traffic.

  In a satellite communications network where a satellite beam covers a number of UTs at any moment, each active UT has a half-duplex pattern with a random offset independent of the other active UTs in beam coverage. For multiple UTs in beam coverage, an aggregate of half-duplex patterns may be created with random offsets. If a large number of active UTs are randomly located within the beam coverage, it is expected that there will be an approximately equal number of UTs per offset and that traffic will be spread approximately evenly over time.

  Assuming that the HD frame has a length of 10 ms, 10 offsets from 0 ms to 9 ms are provided. In the example described above, each of the offsets (0 ms, 1 ms, 2 ms, ... 9 ms) is approximately Will contain an equal number of UTs. If the number of active UTs in beam coverage is relatively small, e.g., less than 10 UTs in beam coverage, each offset of several offsets, e.g. A total of 5 offsets with 2 ms spacing between the pairs may be provided, ie 0 ms, 2 ms, 4 ms, 6 ms, and 8 ms. Again, an approximately equal number of UTs are expected to be found at each of the time offsets.

  In one aspect, system time references and HARQ timelines for communication systems having half-duplex transceivers are established such that these time references and HARQ timelines can be implemented by a scheduler (e.g., scheduler 202) The scheduler may be located at either the gateway or the infrastructure for the UT to operate at the full duplex physical layer. In one aspect, forward link HARQ and return link HARQ acknowledgment rules in a satellite time reference for half-duplex operation may be determined. In one aspect, these forward link and return link HARQ timing rules are constraints that a half-duplex scheduler must follow.

In one aspect, satellite 300 serves as a transponder between gateway 200 and UTs 400 and 401 in the beam coverage of the example satellite 300 shown in FIG. In one aspect, the time reference for the satellite RL receiver only has skewed is or lag time amount equal to the minimum round-trip propagation delay minus T _R2F, T _R2F is above described with respect to the time reference for the satellite FL transmitter As such, system parameters that depend on transition time for transceiver circuit components such as PLLs and PAs to stabilize during transition from transmit mode to receive mode or vice versa.

  8 and 9 are diagrams illustrating examples of HARQ timelines with feeder link delays of about 9.2 ms and about 4 ms, respectively. The propagation delay of the forward link signal and the return link signal between the satellite 300 and the gateway 200 is determined by the distance between the satellite 300 and the gateway 200. In the example shown in FIG. 8, between the rising edge of subframe F of frame k of the gateway transmitter (GW TX) and the rising edge of subframe F of frame k + 1 of the satellite FL transmitter (Sat FSL TX). The feeder link delay is about 9.2 ms.

  In the example shown in FIG. 8, the one-way propagation delay between the satellite 300 and the UT 400 and / or 401 near or near the center of the beam coverage is assumed to be about 4 ms, and thus the center of the beam coverage. Alternatively, the rising edge of subframe F of frame k in the receiver (UT RX @center) of UT400 and / or 401 near the center is delayed by about 4 ms from the rising edge of subframe F of frame k in Sat FSL TX. In contrast, the one-way propagation delay between the satellite 300 and the UT 400 and / or 401 at or near the end of the beam coverage of the satellite 300 is about 5.2 ms.

In the example shown in FIG. 8, a two-way communication timeline between the gateway 200 at or near the center of the beam coverage of the satellite 300 functioning as a transponder and the UTs 400 and / or 401 is shown. The timeline from the rising edge of subframe F of frame k in GW TX to the rising edge of subframe F of frame k + 1 in Sat FSL TX has a propagation time of about 9.2 ms and is a dashed line (F: 1 ^st TX), the timeline from the rising edge of subframe F of frame k + 1 in Sat FSL TX to the rising edge of subframe F of frame k + 1 in UT RX @center is about 4 ms propagation With time, it is indicated by the dashed line (F: 1 ^st TX).

  In UT 400 and / or 401, a process and wait time is given, indicated by a dashed line (F: proc & wait). In frame k + 1 at UT400 and / or 401, subframes are used to separate the reception of the forward link signal at UT at subframe F and the transmission of the return link signal at UT400 and / or 401 at subframe R. G has a guard time. As shown in FIG. 8, the guard time during subframe G is the process and wait time to allow the UT 400 and / or 401 to process the signal or data before subsequent transmission on the return link. Is part of.

In the example shown in FIG. 8, the timeline showing the transmission initiated by UT 400 and / or 401 near or near the center of beam coverage is also the rising edge of subframe R of frame k at the UT transmitter (UT TX @center). From the edge to the rising edge of subframe R of frame k + 1 in the satellite RL receiver (Sat RSL RX) is shown as a dashed line (R: 1 ^st TX). Satellite 300 follows a dashed line (R: 1 ^st TX) that goes from the rising edge of subframe R of frame k + 1 in Sat RSL RX to the rising edge of subframe R of frame k + 2 in the gateway receiver (GW RX). And relay the return link signal from the UT 400 and / or 401 to the gateway. Process and wait time (R: proc & wait) may also be provided at the gateway 200 to allow the gateway 200 to process the signal or data prior to subsequent transmission on the forward link.

  In the example shown in FIG. 8, the non-acknowledgment (NAK) signal goes from the rising edge of subframe R in frame k + 1 at UT TX @center to the rising edge of subframe R in frame k + 2 in Sat RSL RX. And the center of beam coverage or as indicated by the dashed line (F: NAK) from the rising edge of subframe R in frame k + 2 to the rising edge of subframe R in frame k + 3 in GW RX in Sat RSL RX It is transmitted to the gateway 200 via the satellite 300 from the UT 400 and / or 401 near the center.

  Similarly, another NAK signal goes from the rising edge of subframe F of frame k + 3 in GW TX to the rising edge of subframe F of frame k + 4 in Sat FSL TX and frame k + 4 in Sat FSL TX. As shown by the dashed line (R: NAK) from the rising edge of subframe F to the rising edge of subframe F of frame k + 4 in UT RX @center, UT400 and / or via satellite 300 from gateway 200 Sent to 401. In response to a received forward link signal, an acknowledgment (ACK) signal may be sent by the UT 400 and / or 401 instead of a NAK, and similarly, in response to a received return link signal, an ACK The signal may be transmitted by the gateway 200.

In the example shown in FIG. 8, it is assumed that there is a minimum round trip propagation delay of about 8 ms between the satellite 300 and the UTs 400 and / or 401. Therefore, the time reference for Sat RSL RX and Sat FSL TX, as shown by the time difference 8ms-T _R2F between the rising edge of frame k in Sat RSL RX and the rising edge of frame k in Sat FSL TX in FIG. A time delay of 8 ms-T _R2F is introduced between this and the time reference.

In this example, T _{R2F accounts} for a small margin of transition time for it to stabilize, eg 100 μs, plus a small transition time when the half-duplex UT transceiver switches from receive mode to transmit mode or vice versa It is a system parameter. In the example shown in FIG. 8, it is also assumed that UTs 400 and / or 401 require approximately 2 ms of processing time between receiving a forward link packet and sending an ACK or NAK response. The processing time of approximately 2 ms required by the UT 400 and / or 401 is, for example, as shown in FIG. 8, the falling edge of subframe R of frame k + 1 in Sat RSL RX and the frame k in Sat FSL TX. It may be accounted for by providing a time gap of about 2 ms between the +2 rising edge of subframe F.

  The receive and transmit behavior and ACK / NAK response of UT400 and / or 401 (UT RX @edge and UT TX @edge) at or near the end of beam coverage as shown in Figure 8 is the center or center of beam coverage. Similar to nearby UT400 and / or 401 (UT RX @center and UT TX @center). However, the rising edge of subframe F of frame k in UT RX @edge is delayed by about 5.2 ms from the rising edge of subframe F of frame k in Sat FSL TX.

  In this example, UT 400 and / or 401 at or near the end of beam coverage includes the falling edge of subframe R of frame k at UT TX @edge and the subframe of subsequent frame k + 1 at UT RX @edge. A time gap of about 2.6 ms is provided between the rising edge of frame F. Between each subframe F and subframe R of the HD frame at UT400 and / or 401 at or near the end of the beam coverage to correct the time gap of about 2.6ms between two adjacent frames The length of the guard time in subframe G is reduced. In one aspect, the guard time in a given HD frame may be dynamically adjusted by implementing an adaptive special subframe (SSF), described in further detail below.

  FIG. 9 is a diagram illustrating an example of a HARQ timeline for a satellite communication system in which the feeder link delay between the gateway 200 and the satellite 300 is about 4 ms. In this example, there is a time gap of about 4 ms between the rising edge of subframe F of frame k + 1 in GW TX and the rising edge of subframe F of frame k + 1 in Sat FSL TX. In the example shown in FIG. 9, there is a minimum round-trip propagation delay of about 8 ms between the satellite 300 and the UT 400 and / or 401, and the UT 400 and / or 401 receives the forward link packet and transmits the ACK or NAK response. It is also assumed that a processing time of about 2 ms is required between them.

Similar to the example shown in FIG. 8, the time difference between the rising edge of frame k in Sat RSL RX in FIG. 9 and the rising edge of frame k in Sat FSL TX is 8 ms-T _R2F . A time delay of 8ms-T _R2F is provided between the time reference and the time reference for Sat FSL TX, where T _R2F is the transition time plus the half-duplex UT transceiver from receive mode to transmit mode or its On the other hand, when transitioning, it is a system parameter that accounts for a margin for stabilization. In addition, for example, the processing time required by the UT 400 and / or 401 to process received packets and the transition time required by the half-duplex UT transceiver to stabilize between receive and transmit modes To account for the time between the falling edge of subframe R of frame k + 1 in Sat RSL RX and the rising edge of subframe F of frame k + 2 in Sat FSL TX, a time of approximately 2 ms plus T _R2F A gap may be given.

  Based on the example shown in FIGS. 8 and 9, the half-duplex frame pattern at the gateway 200, satellite 300, and UT 400 and / or 401 exceeds the frame shown in FIGS. 8 and 9, for example, frame k + 4 It will be appreciated that it can be repeated in frames beyond k + 5, .... In one aspect, the satellite FL transmission time reference in Sat FSL TX may be set as a zero offset time reference. In one aspect, timelines for gateway transmitters and receivers and UT transmitters and receivers may be derived based on the time delay of each frame relative to the satellite FL transmission time reference. It will be appreciated that the zero offset time reference may be set in other ways to provide the desired relative time delay at the gateway 200 and at the UTs 400 and / or 401.

In one aspect, adaptive special subframe (SSF) to allow the total guard time to be increased or decreased with a corresponding decrease or increase in the total time allocated to the forward link in a given HD frame. Is provided. In the example shown in FIGS. 6 and 7 and described above, a 10 ms HD frame consists of subframes F, S, G, and R having lengths of 3 ms, 1 ms, 2 ms, and 4 ms, respectively. Within frame S, one time segment is allocated for FL F _SSF and another time segment is allocated for time G _SSF . Thus, the total amount of time for the FL in the 10ms HD frame in Figure 6 is 3ms + 0.2ms = 3.2ms, while the total guard time in the 10ms HD frame in Figure 6 is 0.8ms + 2ms = 2.8ms.

In one aspect, the allocation between the amount of time for FL F _{SSF in} the _{SSF and} the amount of guard time G _SSF is such that UT 400 and / or 401 is at or near the center of the beam coverage of satellite 300, i.e. The round-trip propagation delay of the signal between the satellite 300 and the UT 400 and / or 401 is at or near the minimum or near the end of the beam coverage of the satellite 300, i.e. the satellite 300 and the UT 400 and / or Depending on whether the round trip propagation delay of the signal to 401 is at or near the maximum, it may be changed dynamically. In one aspect, between the center and end of beam coverage, a series of SSFs with various allocations of time between F _SSF and G _SSF , while the total amount of SSF remains constant at 1 ms. There is an SSF configuration.

In one aspect, the amount of time allocated to the F _SSF may be increased or decreased in continuous or discrete increments or decrements, and the amount of time allocated to the G _SSF is correspondingly in beam coverage. Depending on the round trip propagation delay between UT 400 and / or 401 and satellite 300, determined by the position of UT 400 and / or 401, may be reduced or increased in continuous or discrete decrements or increments . For example, in a 10ms HD frame, for the UT400 and / or 401 at the center of beam coverage, i.e. with minimal round trip propagation delay, the total length of the SSF may be allocated to the FL, and thus effectively the forward link. , 4ms, 2ms, and 4ms will be allocated to the guard time and return link, respectively.

  On the other hand, in the case of UT400 and / or 401 at the end of beam coverage, i.e. maximum round-trip propagation delay, 0.2ms out of 1ms SSF may be allocated to FL, and 0.8 out of 1ms SSF. ms may be allocated to the guard time, thus effectively allocating 3.2 ms, 2.8 ms, and 4 ms to the forward link, guard time, and return link, respectively, within the HD frame.

In one aspect, a scheduler may be provided to adaptively adjust the time allocation between the F _SSF and G _SSF in the SSF depending on the position of the UT 400 and / or 401 in a given beam coverage. Good. In one aspect, the scheduler may be implemented in a processor as a gateway, eg, as part of the gateway 200 shown in FIG. 1, or as an infrastructure, eg, as part of the infrastructure 106 shown in FIG.

  In one aspect, the scheduler may adaptively adjust the SSF configuration by scheduling an appropriate amount of forward link traffic from the gateway 200 via the satellite 300 to the UTs 400 and / or 401. In one aspect, the UT 400 and / or 401 need only conform to a full duplex frequency division duplex (FDD) timeline specification.

  From a UT perspective, the UT400 and / or 401 may not recognize HD frame patterns designed for half-duplex operation, but may recognize its own half-duplex capability. Yes, a message on the return link, eg, a UT capability message, may inform the network scheduler of its half duplex capability. In one aspect, the UT 400 and / or 401 monitors all subframes as FL subframes unless the subframe is recognized as an RL subframe. In one aspect, the UT 400 and / or 401 follows a scheduler grant for FL reception and RL transmission and follows a full duplex FDD timeline specification for HARQ and grant.

  The scheduler may be implemented in gateway 200 (eg, scheduler 202) or in infrastructure 106. In one aspect, a half-duplex scheduler is required to follow established FL and RL HARQ timing rules. In one aspect, the scheduler may follow a half duplex pattern for a half duplex UT, but is not required to do so.

  For example, 4ms, 2ms, and A 4 ms time allocation may be provided for forward link signal reception, guard time, and return link signal transmission, respectively, in a given HD frame. In this example, the UT 400 and / or 401 can achieve up to 40% beam capacity on the forward link and 40% beam capacity on the return link.

  In one aspect, if there are multiple UTs in beam coverage, the random offset described above may be provided by the scheduler. For example, as explained above, in a 10ms HD frame, if there are a large number of active UTs, e.g. more than 10 UTs in the beam coverage, 10 from 0ms to 9ms increasing in 1ms increments. May be provided in a half-duplex pattern. For a relatively small number of active UTs in beam coverage, eg, less than 10 UTs, 5 offsets from 0 ms to 8 ms increasing in 2 ms increments may be provided. Due to the expected randomness of the various UT locations within the beam coverage over time, it is expected that an approximately equal number of UTs will be found at each of the offsets over time. In one aspect, the scheduler ensures that the aggregation of patterns for all active UTs in beam coverage has a random offset, and random offset to spread approximately equal traffic load across all offsets. May be implemented.

  FIG. 10 is a block diagram illustrating an example of a module for determining the amount of guard time in a half-duplex frame at block 1000. In one aspect, the minimum round trip propagation delay for the UT during satellite beam coverage is determined at block 1002 and the maximum round trip propagation delay for the UT is determined at block 1004. In one aspect, the minimum round trip propagation delay is the round trip delay of signal propagation when the UT is at the center of beam coverage. In another aspect, the maximum round trip propagation delay is the round trip delay of signal propagation when the UT is at the end of beam coverage.

  Referring to FIG. 10, the maximum round trip propagation delay difference is determined at block 1008 based on the minimum and maximum round trip propagation delays determined at block 1002 and block 1004, respectively. In one aspect, the maximum round trip propagation delay difference is determined by subtracting the minimum round trip propagation delay from the maximum round trip propagation delay.

  When the transceiver switches from receive mode to transmit mode and vice versa, the transition time for the circuit components of the half-duplex transceiver, such as a phase-locked loop (PLL) or power amplifier (PA), to stabilize is block 1006. To be determined. In one aspect, a margin may be included in the transition time for the half-duplex transceiver to switch from receive mode to transmit mode and vice versa. Based on the maximum round trip propagation delay difference and the transition time for the transceiver to switch from receive mode to transmit mode and vice versa, the guard time between the forward link and the return link in a half-duplex frame at UT is blocked Determined at 1010. In one aspect, the guard time is determined by the sum of the maximum round trip propagation delay difference, the transition time from the reception mode to the transmission mode, and the transition time from the transmission mode to the reception mode.

  FIG. 11 is a block diagram illustrating an example of a module for skewing the return link time reference with respect to the forward link time reference in block 1100. In one aspect, a half-duplex transceiver circuit configuration including, for example, a PLL or PA, when a minimum round trip propagation delay is determined at block 1102 and the transceiver switches from transmit mode to receive mode or vice versa at block 1104. The transition time for the element to stabilize is determined. As explained above, in one aspect, the minimum round trip propagation delay is the round trip delay of signal propagation when a UT in the beam coverage of the satellite communicates with the satellite at the center of the beam coverage.

Referring to FIG. 11, at block 1106, a system parameter, _TR2F, is determined based on the transition time. In one aspect, the system parameter T _R2F may be determined by adding a margin to the transition time for the half-duplex transceiver to transition from transmit mode to receive mode or vice versa. Based on the minimum round trip propagation delay and the system parameter T _R2F , the amount of return link time reference skewing or time lag relative to the forward link time reference is determined at block 1108.

In one aspect, the amount of skewing or time lag is determined by subtracting the system parameter _TR2F from the minimum round trip propagation delay. In one aspect, the forward link time reference at the satellite forward link transmitter may be set as a zero offset time reference, and the return link time reference at the satellite return link receiver is the forward link time reference at the satellite forward link transmitter. It may be skewed or delayed in time.

FIG. 12 is a block diagram illustrating an example of a module for determining a half-duplex transmission / reception pattern at a user terminal (UT) in block 1200. In one aspect, the forward link time segment F _{SSF in} the special subframe (SSF) of the HD frame is allocated at block 1202 and the guard time segment G _{SSF in} the SSF of the HD frame is allocated at block 1204. In the above aspect, the total length of the SSF remains constant at 1 ms in the 10 ms HD frame, but the proportion of the forward link time segment F _{SSF and} the proportion of the guard time segment G _{SSF in} the _SSF are required in the HD frame. May be dynamically adjusted based at least in part on the amount of total guard time taken.

As shown in FIGS. 6 and 7 and described above, the forward link time segment F _{SSF in} subframe S follows immediately after subframe F in the HD frame and is the total duration for forward link reception by the UT. Is the sum of the duration of subframe F and the duration of F _SSF in subframe S. Similarly, the guard time segment G _{SSF in} subframe S is immediately before subframe G in the HD frame, and the total duration of the guard time is the duration of subframe G and the continuation of G _SSF in subframe S. It is the sum of time. In the example shown in FIG. 6, the duration of subframe R for return link transmission by UT remains constant at 4 ms. Referring to FIG. 12, the forward link time, guard time, and return link time in the HD frame are allocated at block 1206.

  FIG. 13 is a block diagram illustrating an example of the random offset scheduler 1300. In one aspect, the number of offsets based on the number of active UTs found in the satellite beam coverage is determined by the module in block 1302. In one aspect, the offsets are assigned at equal intervals in time by the modules in block 1304. If the number of active UTs in the beam coverage is large, e.g. more than 10 UTs and the HD frame length is 10ms, 10 offsets from 0ms to 9ms as explained above Up to 1 ms may be provided. For example, if there are fewer than 10 active UTs, as described above, a smaller number of offsets may be provided, eg, 5 offsets in increments of 2 ms from 0 ms to 8 ms.

  In one aspect, the random offset scheduler 1300 may be implemented in a gateway such as the gateway 200 shown in FIG. 1 or in an infrastructure such as the infrastructure 106 shown in FIG. In one aspect, it is not necessary for the UT in the satellite beam coverage to be aware of the presence of the random offset scheduler 1300 in the gateway 200 or infrastructure 106. The UT need only apply the time offset determined by the random offset scheduler 1300 for that particular UT. Referring to FIG. 13, the random offset scheduler 1300 includes a module in block 1306 to determine whether the aggregate pattern for all active UTs in beam coverage has a random offset. Based on the determination of the aggregation pattern, the module in block 1308 of the random offset scheduler 1300 spreads approximately equal traffic load across all offsets.

  FIG. 14 is a block diagram illustrating an example of an adaptive special subframe (SSF) scheduler at block 1400. In one aspect, adaptive SSF scheduler 1400 may be implemented in a gateway such as gateway 200 shown in FIG. 1 or in an infrastructure such as infrastructure 106 shown in FIG. In one aspect, it is not necessary that a UT in satellite beam coverage be aware of the presence of an adaptive SSF scheduler 1400 in the gateway 200 or infrastructure 106.

Referring to FIG. 14, a module in block 1402 of the adaptive SSF scheduler 1400 moves the forward link time segment F _SSF based on the position of the UT relative to the satellite, which determines the distance between the UT and the satellite and thus the propagation delay. To adjust. In one aspect, adaptive SSF scheduler 1400 also includes a module in block 1404 to adjust guard time segment G _SSF in adaptive SSF scheduler 1400 based on the position of the UT in the beam coverage of the satellite.

In one aspect, since the total length of adaptive SSF scheduler 1400 remains constant, an increase in guard time segment G _SSF requires a decrease in forward link time segment F _SSF and vice versa. Based on dynamically adjusted F _SSF and G _SSF , the total time for forward link reception and the total guard time between forward link reception and return link transmission in HD frame for UT is blocked Determined by the module in 1406. In one aspect, the total time for forward link reception is determined by adding the length of time of F _SSF to the length of time of forward link subframe F in the HD frame shown in FIG. The guard time is determined by adding the length of time of G _SSF to the length of time of guard subframe G in the HD frame shown in FIG.

  The functionality of the modules of FIGS. 10-14 may be implemented in a variety of ways consistent with the teachings herein. In some designs, the functionality of these modules may be implemented as one or more electrical components. In some designs, the functionality of these modules may be implemented as a processing system that includes one or more processor components. In some designs, the functionality of these modules may be implemented using, for example, at least a portion of one or more integrated circuits (eg, ASICs). As discussed herein, an integrated circuit may include a processor, software, other related components, or some combination thereof. Thus, the functionality of different modules may be implemented, for example, as different subsets of an integrated circuit, may be implemented as different subsets of a set of software modules, or a combination thereof. It will also be appreciated that a given subset (eg, of an integrated circuit and / or set of software modules) may implement at least some of the functionality associated with more than one module. Further, it will be appreciated that the modules and functions described herein may be implemented in one or more elements of a satellite communication system (e.g., gateway, infrastructure, satellite, and / or UT). . For example, in some aspects, functionality may be shared between multiple elements (eg, gateways and infrastructure) of a satellite communication system that are in communication with each other. Accordingly, the description provided herein is only an example.

  In addition, the components and functions represented by FIGS. 10-14 and other components and functions described herein may be implemented using any suitable means. Such means may also be implemented, at least in part, using corresponding structures as taught herein. For example, the components described above in conjunction with the “module for” component of FIGS. 10-14 may correspond to a similarly designated “means for” function. Thus, in some aspects, one or more of such means uses one or more of processor components, integrated circuits, or other suitable structures taught herein. May be implemented.

  In view of the above disclosure, it will be appreciated that certain aspects can assist in the methods for performing the various functions disclosed herein. For example, FIG. 15 is a flowchart illustrating a method for determining a return link time reference time lag relative to a forward link time reference in a satellite communication system. At block 1502, a minimum round trip propagation delay of the signal between the ground station and the satellite is determined. At block 1504, a transition time for the ground station half-duplex transceiver to switch between transmit mode and receive mode is determined. At block 1506, system parameters are determined based on the transition time for the half-duplex transceiver to switch between transmit mode and receive mode. At block 1508, the return link time reference time lag relative to the forward link time reference is determined based on the minimum round trip propagation delay and system parameters. This method may be implemented in a satellite communication system 100 as shown in FIG. The satellite communication system 100 can include a satellite 300 and at least one ground station (eg, UT400, UT401) having a half-duplex transceiver in the beam coverage of the satellite 300.

  In another aspect, FIG. 16 is a flowchart illustrating a method for determining a guard time between reception and transmission in a half-duplex transceiver. At block 1602, the maximum round trip propagation delay of the signal between the half duplex transceiver and the satellite is determined. At block 1604, the minimum round trip propagation delay of the signal between the half duplex transceiver and the satellite is determined. At block 1606, a maximum round trip propagation delay difference is determined based on the maximum round trip propagation delay and the minimum round trip propagation delay. In block 1608, a transition time for the half-duplex transceiver to switch between transmit mode and receive mode is determined. At block 1610, a guard time is determined based on the maximum round trip propagation delay difference and the transition time for the half duplex transceiver to switch between transmit and receive modes. This method may be implemented in a satellite communication system 100 as shown in FIG. The satellite communication system 100 can include a satellite 300 and at least one ground station (eg, UT400, UT401) having a half-duplex transceiver in the beam coverage of the satellite 300.

  In another aspect, FIG. 17 is a flowchart illustrating a method for determining a forward link duration and a guard duration in a half-duplex frame in a satellite communication system. At block 1702, forward link time segments are allocated in special subframes of a half-duplex frame. At block 1704, guard time segments are allocated in special subframes. At block 1706, the forward link duration in the half-duplex frame is determined based on the forward link time segment in the special subframe. At block 1708, the guard duration in the half-duplex frame is determined based on the guard time segment in the special subframe. This method may be implemented in a satellite communication system 100 as shown in FIG. The satellite communication system 100 may include a gateway 200 having a scheduler 202, a satellite 300, and at least one ground station (eg, UT400, UT401) having a half-duplex transceiver in the beam coverage of the satellite 300.

  In another aspect, FIG. 18 is a flowchart illustrating a method for scheduling time offsets for multiple user terminals during satellite beam coverage in a satellite communication system. At block 1802, the number of time offsets is determined based on the number of active user terminals in beam coverage. At block 1804, equally spaced time offsets are assigned based on the number of time offsets. At block 1806, it is determined whether the aggregate pattern for active user terminals in beam coverage has a random offset. At block 1808, approximately equal traffic loads are spread over time for active user terminals. This method may be implemented in a satellite communication system 100 as shown in FIG. The satellite communication system 100 may include a gateway 200 having a scheduler 202, a satellite 300, and a plurality of user terminals (eg, UT400, UT401) in the beam coverage of the satellite 300.

  Those skilled in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description are voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, light fields or optical particles, or It may be expressed by any combination of.

  Moreover, those skilled in the art will implement various exemplary logic blocks, modules, circuits, and algorithm steps described in connection with aspects disclosed herein as electronic hardware, computer software, or a combination of both. Let's understand that there is a case. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functions are implemented as hardware or software depends on the specific application and design constraints imposed on the overall system. Those skilled in the art can implement the described functions in a variety of ways for each specific application, but such implementation judgment should not be construed as causing a departure from the scope of the present disclosure. Absent.

  The methods, sequences, or algorithms described with respect to the aspects disclosed herein may be embodied directly in hardware, in software modules executed by a processor, or in a combination of the two. Software modules reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art Can do. An example storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.

  Accordingly, one aspect of the present disclosure can include a computer readable medium embodying one or more methods disclosed herein relating to half-duplex data transmission in a non-geostationary satellite communication system. . Accordingly, the present disclosure is not limited to the illustrated examples and any means for performing the functions described herein are included in the aspects of the present disclosure.

  While the above disclosure represents exemplary embodiments, it should be noted that various changes and modifications can be made herein without departing from the scope of the appended claims. The functions, steps or activities of a method claim according to aspects described herein do not have to be performed in any particular order unless explicitly stated otherwise. Further, although elements may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.

100 satellite communication systems
106 Infrastructure
108 Internet
110 Public switched telephone network (PSTN)
200 gateways
201 gateway
202 scheduler
205 Antenna
210 RF subsystem
212 RF transceiver
214 RF controller
216 Antenna controller
220 Digital subsystem
222 Digital receiver module
224 Digital transmitter module
226 Baseband (BB) processor
228 Control (CTRL) processor
230 PSTN interface
240 Local Area Network (LAN) interface
245 Gateway interface
250 gateway controller
251 Local time, frequency, and location criteria
300 satellites
301F Forward link (FL)
301R return link (RL)
310 Forward transponder
311 First bandpass filter
312 First Low Noise Amplifier (LNA)
313 Frequency converter
314 Second LNA
315 Second bandpass filter
316 Power Amplifier (PA)
320 Return transponder
321 First bandpass filter
322 1st LNA
323 frequency converter
324 2nd LNA
325 Second bandpass filter
326 PA
330 oscillator
340 controller
352 Forward link antenna
361 Return link antenna
362 antenna
400 User terminal (UT)
401 UT
414 analog receiver
416 digital data receiver
418 Searcher Receiver
420 User terminal control processor
422 Digital baseband circuit
426 transmit modulator
428 Digital Transmit Power Controller
430 analog transmit power amplifier
432 memory
434 Local time, frequency, and / or location criteria
450 UE interface circuit
500 User equipment (UE)
501 UE
502 LAN interface
504 antenna
506 Wide Area Network (WAN) transceiver
508 Wireless Local Area Network (WLAN) transceiver
510 Satellite Positioning System (SPS) receiver
512 processor
514 Motion sensor
516 memory
518 data
520 instructions
522 User interface
524 Microphone / Speaker
526 keypad
528 display

Claims (32)

A method for determining a time lag of a return link time reference with respect to a forward link time reference in a satellite communication system, comprising:
Determining a minimum round-trip propagation delay of the signal between the ground station and the satellite;
Determining a transition time for the ground station half-duplex transceiver to switch between transmit mode and receive mode;
Determining system parameters based on the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode;
Determining the time lag of the return link time reference relative to the forward link time reference based on the minimum round trip propagation delay and the system parameter.   The method of claim 1, further comprising determining a guard time between reception and transmission at the half-duplex transceiver. Determining the guard time between reception and transmission at the half-duplex transceiver;
Determining a maximum round-trip propagation delay of a signal between the ground station and the satellite;
Determining a maximum round trip propagation delay difference based on the maximum round trip propagation delay and the minimum round trip propagation delay;
Determining the guard time based on the maximum round-trip propagation delay difference and the transition time for the half-duplex transceiver to switch between the transmission mode and the reception mode. The method described.   The method of claim 1, wherein the ground station includes a user terminal.   The method of claim 1, wherein the satellite comprises a non-geostationary satellite. An apparatus configured to determine a return link time reference time lag relative to a forward link time reference in a satellite communication system, comprising:
At least one processor;
At least one memory coupled to the at least one processor, the at least one processor and the at least one memory comprising:
Determining the minimum round-trip propagation delay of the signal between the ground station and the satellite;
Determining a transition time for the ground station half-duplex transceiver to switch between transmit mode and receive mode;
Determining a system parameter based on the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode;
An apparatus configured to determine the time lag of the return link time reference relative to the forward link time reference based on the minimum round trip propagation delay and the system parameter. An apparatus for determining a return link time reference time lag relative to a forward link time reference in a satellite communication system, comprising:
Means for determining a minimum round-trip propagation delay of the signal between the ground station and the satellite;
Means for determining a transition time for the half-duplex transceiver at the ground station to switch between transmit mode and receive mode;
Means for determining system parameters based on the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode;
Means for determining the time lag of the return link time reference relative to the forward link time reference based on the minimum round trip propagation delay and the system parameter. A computer readable medium comprising at least one instruction for causing a computer or processor to perform a method for determining a time lag of a return link time reference to a forward link time reference in a satellite communication system, wherein the at least one instruction is ,
Instructions for determining the minimum round-trip propagation delay of the signal between the ground station and the satellite;
Instructions for determining a transition time for the ground station half-duplex transceiver to switch between transmit mode and receive mode;
Instructions for determining system parameters based on the transition time for the half-duplex transceiver to switch between the transmit mode and the receive mode;
Instructions for determining the time lag of the return link time reference relative to the forward link time reference based on the minimum round trip propagation delay and the system parameter. A method for determining a guard time between reception and transmission in a half-duplex transceiver, comprising:
Determining a maximum round-trip propagation delay of a signal between the half-duplex transceiver and a satellite;
Determining a minimum round-trip propagation delay of a signal between the half-duplex transceiver and the satellite;
Determining a maximum round trip propagation delay difference based on the maximum round trip propagation delay and the minimum round trip propagation delay;
Determining a transition time for the half-duplex transceiver to switch between transmit mode and receive mode;
Determining the guard time based on the maximum round trip propagation delay difference and the transition time for the half-duplex transceiver to switch between the transmission mode and the reception mode.   10. The method of claim 9, wherein the half-duplex transceiver comprises a user terminal transceiver.   The method of claim 9, wherein the satellite comprises a non-geostationary satellite. An apparatus configured to determine a guard time between reception and transmission in a half-duplex transceiver comprising:
At least one processor;
At least one memory coupled to the at least one processor, the at least one processor and the at least one memory comprising:
Determining a maximum round-trip propagation delay of a signal between the half-duplex transceiver and a satellite;
Determining a minimum round-trip propagation delay of a signal between the half-duplex transceiver and the satellite;
Determining a maximum round trip propagation delay difference based on the maximum round trip propagation delay and the minimum round trip propagation delay;
Determining a transition time for the half-duplex transceiver to switch between transmit mode and receive mode;
And determining the guard time based on the maximum round-trip propagation delay difference and the transition time for the half-duplex transceiver to switch between the transmission mode and the reception mode. ,apparatus. An apparatus for determining a guard time between reception and transmission in a half-duplex transceiver, comprising:
Means for determining a maximum round-trip propagation delay of a signal between the half-duplex transceiver and a satellite;
Means for determining a minimum round-trip propagation delay of a signal between the half-duplex transceiver and the satellite;
Means for determining a maximum round trip propagation delay difference based on the maximum round trip propagation delay and the minimum round trip propagation delay;
Means for determining a transition time for the half-duplex transceiver to switch between transmit mode and receive mode;
Means for determining the guard time based on the maximum round-trip propagation delay difference and the transition time for the half-duplex transceiver to switch between the transmission mode and the reception mode. A computer readable medium comprising at least one instruction for causing a computer or processor to perform a method for determining a guard time between reception and transmission in a half-duplex transceiver, the at least one instruction comprising:
Instructions for determining a maximum round-trip propagation delay of a signal between the half-duplex transceiver and a satellite;
Instructions for determining a minimum round-trip propagation delay of a signal between the half-duplex transceiver and the satellite;
Instructions for determining a maximum round trip propagation delay difference based on the maximum round trip propagation delay and the minimum round trip propagation delay;
Instructions for determining a transition time for the half-duplex transceiver to switch between transmit mode and receive mode;
Instructions for determining the guard time based on the maximum round trip propagation delay difference and the transition time for the half duplex transceiver to switch between the transmission mode and the reception mode. Medium. A method for determining a forward link duration and a guard duration in a half-duplex frame in a satellite communication system, comprising:
Allocating forward link time segments in special subframes of the half-duplex frame;
Allocating guard time segments in the special subframes;
Determining the forward link duration in the half-duplex frame based on the forward link time segment in the special subframe;
Determining the guard duration in the duplex frame based on the guard time segment in the special subframe.   16. The method of claim 15, wherein the half-duplex frame further includes a forward link subframe that precedes the special subframe and a guard subframe that follows the special subframe.   17. The method of claim 16, wherein determining the forward link duration in the half-duplex frame comprises adding the forward link time segment in the special subframe to the forward link subframe.   17. The method of claim 16, wherein determining the guard duration in the half-duplex frame comprises adding the guard time segment in the special subframe to the guard subframe.   16. The method of claim 15, wherein the method is performed by an adaptive special subframe (SSF) scheduler.   The method of claim 19, wherein the adaptive SSF scheduler is in a gateway.   The method of claim 15, wherein the satellite communication system includes at least one ground station.   16. The method of claim 15, wherein the satellite communication system includes a satellite that is a non-geostationary satellite. An apparatus configured to determine a forward link duration and a guard duration in a half-duplex frame in a satellite communication system, comprising:
At least one processor;
At least one memory coupled to the at least one processor, the at least one processor and the at least one memory comprising:
Allocating a forward link time segment in a special subframe of the half-duplex frame;
Allocating guard time segments in the special subframes;
Determining the forward link duration in the half-duplex frame based on the forward link time segment in the special subframe;
An apparatus configured to determine the guard duration in the half-duplex frame based on the guard time segment in the special subframe. An apparatus for determining a forward link duration and a guard duration in a half-duplex frame in a satellite communication system, comprising:
Means for allocating forward link time segments in special subframes of the half-duplex frame;
Means for allocating guard time segments in the special subframe;
Means for determining the forward link duration in the half-duplex frame based on the forward link time segment in the special subframe;
Means for determining the guard duration in the half-duplex frame based on the guard time segment in the special subframe. A computer-readable medium comprising at least one instruction for causing a computer or processor to execute a method for determining a forward link duration and a guard duration in a half-duplex frame in a satellite communication system, the computer comprising: Two instructions
Instructions for allocating forward link time segments in special subframes of the half-duplex frame;
Instructions for allocating guard time segments in the special subframe;
Instructions for determining the forward link duration in the half-duplex frame based on the forward link time segment in the special subframe;
Instructions for determining the guard duration in the half-duplex frame based on the guard time segment in the special subframe. A method for scheduling time offsets of a plurality of user terminals during satellite beam coverage in a satellite communication system, comprising:
Determining a number of time offsets based on the number of active user terminals in the beam coverage;
Allocating equally spaced time offsets based on the number of time offsets;
Determining whether an aggregate pattern for the active user terminal in the beam coverage has a random offset;
Spreading substantially equal traffic load over time for said active user terminals.   27. The method of claim 26, wherein the method is performed by a random offset scheduler.   28. The method of claim 27, wherein the random offset scheduler is at a gateway.   27. The method of claim 26, wherein the satellite comprises a non-geostationary satellite. An apparatus configured to schedule time offsets of a plurality of user terminals during satellite beam coverage in a satellite communication system, comprising:
At least one processor;
At least one memory coupled to the at least one processor, the at least one processor and the at least one memory comprising:
Determining the number of time offsets based on the number of active user terminals in the beam coverage;
Allocating equally spaced time offsets based on the number of time offsets;
Determining whether an aggregate pattern for the active user terminal in the beam coverage has a random offset;
An apparatus configured to spread substantially equal traffic load over time for the active user terminal. An apparatus for scheduling time offsets of a plurality of user terminals during satellite beam coverage in a satellite communication system, comprising:
Means for determining the number of time offsets based on the number of active user terminals in the beam coverage;
Means for allocating equally spaced time offsets based on the number of time offsets;
Means for determining whether an aggregate pattern for the active user terminal in the beam coverage has a random offset;
Means for spreading substantially equal traffic loads over time for said active user terminals. A computer readable medium comprising at least one instruction for causing a computer or processor to perform a method of scheduling a time offset of a plurality of user terminals during satellite beam coverage in a satellite communication system, wherein the at least one instruction is ,
Instructions for determining the number of time offsets based on the number of active user terminals in the beam coverage;
Instructions for allocating equally spaced time offsets based on the number of time offsets;
Instructions for determining whether an aggregate pattern for the active user terminal in the beam coverage has a random offset;
And a computer readable medium comprising instructions for spreading an approximately equal traffic load over time for the active user terminal.

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